What causes a SPN 334 code?

SPN 334 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a SPN 334 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 334 active.

How do I fix SPN 334?

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBDIY

J1939 SPN

SPN 334

J1939 SPN 334 — Fuel/Air parameter

What it means

SPN 334 indicates a Fuel/Air Ratio Control error. The engine control module (ECM) oversees the balance of air flow and fuel delivery to ensure stoichiometric or programmed combustion efficiency; this code triggers when that balance is disrupted.